Torrent just does not work with selfish/not caring users who quit torrent client right after downloading, so no one can download the file from them. Or even worse, with torrent client configured to not seed at all.
So now all who have the whole file, have left. There is only half of the file available along remaining seeders.
Torrent works great with users who have the client running in background seeding all what they have downloaded in the past.
Of course, if you live in a country with limited freedom (like USA) you have to be careful what you are seeding, means to avoid stuff owned by few largest copyright owner corporations with abundant lawyer departments.